JP5765211B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus.

  In a refrigeration apparatus such as an air conditioner, the optimum refrigerant amount during cooling operation and the optimum refrigerant amount during heating operation are often different, and the capacity of the heat source side heat exchanger that functions as a refrigerant radiator during cooling operation, The capacity of the use-side heat exchanger that functions as a refrigerant radiator during the heating operation is often different. In conventional refrigeration systems, the capacity of the heat source side heat exchanger is often larger than the capacity of the use side heat exchanger, and refrigerant that cannot be accommodated by the use side heat exchanger during heating operation is temporarily stored in, for example, an accumulator. It is stored in.

  On the other hand, recently, there is a small and high performance heat exchanger as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 6-143991).

  When such a small heat exchanger is adopted as the heat source side heat exchanger of the refrigeration apparatus, the capacity of the heat source side heat exchanger becomes smaller than the capacity of the use side heat exchanger, contrary to the conventional refrigeration apparatus. In the pump-down operation in which the refrigeration apparatus is operated in the cooling operation cycle, there is a possibility that a situation may occur in which the refrigerant cannot be stored in the heat source side unit.

  The subject of this invention is providing the refrigeration apparatus which can collect a refrigerant | coolant suitably by the pump down driving | operation to the heat-source side unit which has an accumulator.

The refrigeration apparatus according to the first aspect of the present invention includes a heat source side unit, a use side unit, and a control unit. The heat source side unit includes a liquid refrigerant side closing valve, a gas refrigerant side closing valve, a compressor, a heat source side heat exchanger, a heat source side fan that blows air to the heat source side heat exchanger, an expansion valve, and a compressor. And an accumulator provided in the suction side pipe. The usage-side unit has a usage-side heat exchanger and a usage-side fan that blows air to the usage-side heat exchanger . One end of the usage side unit is connected to the liquid refrigerant side closing valve via the liquid refrigerant communication pipe, and the other end is connected to the gas refrigerant side closing valve via the gas refrigerant communication pipe. The control unit performs a pump-down operation for collecting the refrigerant in the heat source side unit. In the pump down operation, the control unit sequentially performs an activation step, a first liquid reservoir step, and a second liquid reservoir step. In the first liquid reservoir step after the startup step, the compressor is operated at a lower rotational speed than the rotational speed of the compressor in the startup step, and the use-side fan that has been rotating in the startup step is stopped, so that the liquid refrigerant With the side shut-off valve opened, the wet gas refrigerant is drawn from the use side heat exchanger via the gas refrigerant communication pipe, and the accumulator stores the refrigerant. In the second liquid reservoir step after the first liquid reservoir step, the refrigerant is sent from the compressor to the heat source side heat exchanger with the liquid refrigerant side closing valve closed, and the refrigerant is put into the heat source side heat exchanger. To accumulate.

  When collecting refrigerant in the heat source side unit by pump-down operation, conventionally, since the refrigerant is sent from the compressor to the heat source side heat exchanger with the liquid refrigerant side shut-off valve closed, the heat source side heat exchanger has Although the refrigerant accumulates, the refrigerant hardly accumulates in the accumulator provided in the suction side piping of the compressor.

  Therefore, in the refrigeration apparatus according to the present invention, the first liquid storage step for storing the refrigerant in the accumulator is performed prior to the second liquid storage step performed with the liquid refrigerant side closing valve closed. As described above, in the pump down operation, the liquid refrigerant side closing valve is opened to draw the wet gas refrigerant from the use side heat exchanger, the liquid refrigerant side closing valve is closed and the refrigerant is transferred to the heat source side heat exchanger. Since the refrigerant is stored in each part of the heat source side unit in the order of the second liquid storage step for sending the refrigerant, the refrigeration apparatus according to the present invention avoids a situation where the refrigerant cannot be stored in the heat source side unit. be able to.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, and the expansion valve is an electric valve. The expansion valve is disposed between the heat source side heat exchanger and the liquid refrigerant side closing valve. Then, in the pump-down operation, the control unit executes the pressure lowering step after the first liquid reservoir step and before executing the second liquid reservoir step. In the pressure reduction step, the opening of the expansion valve is changed to gradually reduce the refrigerant pressure in the accumulator.

  In the refrigeration apparatus according to the present invention, the refrigerant is accumulated in the accumulator in the first liquid reservoir step. From the first liquid reservoir step in which the liquid refrigerant side shutoff valve is opened to the second liquid reservoir step in which the liquid refrigerant side shutoff valve is closed. If it moves abruptly, the liquid refrigerant stored in the accumulator may foam under reduced pressure. In order to avoid this, in the refrigeration apparatus according to the second aspect of the present invention, a pressure drop step is provided between the first liquid reservoir step and the second liquid reservoir step. In the pressure lowering step, the refrigerant pressure in the accumulator is lowered step by step using an electric expansion valve, so that the liquid refrigerant in the accumulator accumulated in the first liquid reservoir step foams and the amount of refrigerant in the accumulator is reduced. It can suppress that it decreases.

  The refrigeration apparatus according to the third aspect of the present invention is the refrigeration apparatus according to the second aspect, and the liquid refrigerant side closing valve is a manual valve. And a control part makes the opening degree of an expansion valve the lower limit when starting a 2nd liquid reservoir step or just before the start of a 2nd liquid reservoir step. Further, the control unit notifies the operator of the closing operation of the liquid refrigerant side closing valve so that the liquid refrigerant side closing valve is closed after the opening degree of the expansion valve reaches the lower limit value.

  Here, when the second liquid reservoir step is started, or immediately before the start of the second liquid reservoir step, the opening of the expansion valve that has been gradually closed in the pressure reduction step is set to the lower limit value. Thereby, in a 2nd liquid reservoir step, it is suppressed that the refrigerant | coolant sent to the heat-source side heat exchanger flows toward the utilization side unit. In addition, the control unit notifies the operator of the closing operation of the liquid refrigerant side closing valve, but the timing of the notification is the closing operation of the liquid refrigerant side closing valve after the opening degree of the expansion valve reaches the lower limit value. Is set to a timing at which As a result, a situation in which the liquid refrigerant side closing valve is manually closed before the opening degree of the expansion valve reaches the lower limit value is avoided, and the reduced pressure foaming suppression function of the pressure lowering step works appropriately.

  In addition, if there exists a display display, you may perform notification with respect to an operator, and you may perform it using lighting components, such as LED.

  A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to the second or third aspect, wherein the control unit terminates the pressure reduction step after elapse of a predetermined time or the suction side piping of the compressor The change of the opening degree of the expansion valve in the pressure drop step and the end of the pressure drop step are determined based on the output value of the pressure sensor provided in the step.

  Although it is preferable to provide a pressure drop step in order to suppress decompression foaming, if the pressure drop step takes too much time, the total time required for the pump-down operation becomes long. Here, a predetermined period of time during which decompression foaming is suppressed is examined in advance by a test or the like, and the pressure reduction step is terminated after the predetermined time has elapsed, or the decompression foaming is not performed from the pressure measurement value of the suction side piping of the compressor. Thus, the pressure reduction step is performed by any method of determining the end of the pressure reduction step while changing the opening of the expansion valve. For this reason, the situation where the time of a pressure fall step becomes long can be avoided.

  The refrigeration apparatus according to the fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects, and the control unit ends the first liquid reservoir step after elapse of a predetermined time.

  In the first liquid reservoir step, the wet gas refrigerant is drawn from the use-side heat exchanger with the liquid refrigerant side shut-off valve opened, and the accumulator stores the refrigerant. However, such a state in which the wet gas refrigerant is drawn continues for a long time. Then, there is a risk that the liquid refrigerant that cannot be stored in the accumulator will flow to the compressor. Therefore, here, a predetermined time during which the refrigerant accumulates in the accumulator is examined in advance by a test or the like, and the first liquid storage step is terminated after the predetermined time has elapsed. Thereby, the malfunction that a liquid refrigerant flows into a compressor from an accumulator and a compressor is damaged can be avoided.

  A refrigeration apparatus according to a sixth aspect of the present invention is the refrigeration apparatus according to any one of the first to fifth aspects, wherein the control unit performs a startup step before the first liquid reservoir step in the pump down operation. Let it run. In the starting step, the compressor is operated at a higher rotational speed than the rotational speed of the compressor in the first liquid reservoir step.

  Here, before performing the first liquid reservoir step that is different from the normal operation of drawing the wet gas refrigerant from the use side heat exchanger, the compressor is operated at a higher rotational speed than the rotational speed of the compressor in the first liquid reservoir step. The start-up step close to the normal operation is performed. For this reason, the behavior of the refrigerant in the first liquid reservoir step is stabilized, and the steps after the first liquid reservoir step are satisfactorily executed without being greatly affected by the state of the refrigeration apparatus and the refrigerant before the pump-down operation. become.

  A refrigeration apparatus according to a seventh aspect of the present invention is the refrigeration apparatus according to any one of the first to sixth aspects, and the volume of the heat source side heat exchanger is a volume Vho. The volume of the use side heat exchanger is the volume Vhi and is larger than the volume Vho.

  When the volume Vhi of the use side heat exchanger is larger than the volume Vho of the heat source side heat exchanger, there is a possibility that the capacity of the refrigerant circuit of the heat source side unit is insufficient even if the pump down operation for collecting the refrigerant in the heat source side unit is performed. is there. However, in the refrigeration apparatus according to the present invention, the refrigerant in the accumulator is stored in the first liquid storage step, and the refrigerant in the heat source side heat exchanger is stored in the second liquid storage step, so that the accumulator of the heat source side unit is effectively used. Therefore, it is possible to avoid the problem that the refrigerant is not collected in the heat source side unit by the pump down operation.

  In the refrigeration apparatus according to the first aspect of the present invention, the refrigerant is stored in the accumulator in the first liquid storage step of opening the liquid refrigerant side closing valve and drawing the wet gas refrigerant from the use side heat exchanger. The situation where it cannot be accommodated can be avoided.

  In the refrigeration apparatus according to the second aspect of the present invention, it is possible to suppress the liquid refrigerant in the accumulator accumulated in the first liquid reservoir step from foaming and reducing the amount of refrigerant in the accumulator.

  In the refrigeration apparatus according to the third aspect of the present invention, a situation in which the liquid refrigerant side closing valve is manually closed before the opening degree of the expansion valve reaches the lower limit is avoided, and the decompression foaming suppression function of the pressure reduction step is prevented. Will work properly.

  In the refrigeration apparatus according to the fourth aspect of the present invention, it is possible to avoid a situation in which the time of the pressure reduction step becomes long.

  In the refrigeration apparatus according to the fifth aspect of the present invention, the problem that the liquid refrigerant flows from the accumulator to the compressor and the compressor is damaged can be reliably avoided.

  In the refrigeration apparatus according to the sixth aspect of the present invention, the behavior of the refrigerant in the first liquid storage step is stabilized, and the pump down operation is favorably performed without being affected by the state of the refrigeration apparatus and the refrigerant before the pump down operation. Will be executed.

  In the refrigeration apparatus according to the seventh aspect of the present invention, the volume Vhi of the use side heat exchanger is larger than the volume Vho of the heat source side heat exchanger, but since the accumulator of the heat source side unit is effectively used, the pump down operation is performed. Thus, it is possible to avoid the problem that the refrigerant cannot be collected in the heat source side unit.

The refrigerant circuit figure of the air conditioning apparatus which concerns on one Embodiment of this invention. The perspective view of an outdoor heat exchanger. The longitudinal cross-sectional view of an outdoor heat exchanger. The figure which shows the refrigerant | coolant path | pass of an outdoor heat exchanger. The figure which shows one state when the liquid refrigerant is stored in the outdoor heat exchanger and the large diameter pipe in the second liquid storage step. The block diagram of the control part of an air conditioning apparatus. The figure which shows the control state etc. of the control object apparatus in each step of a pump down driving | operation. Schematic flow diagram of pump down operation. The perspective view of the outdoor heat exchanger which concerns on a modification.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following embodiment is one specific example of the present invention, and does not limit the technical scope of the present invention.

(1) Configuration of Air Conditioner (1-1) Overall Configuration FIG. 1 is a diagram illustrating a refrigerant circuit of an air conditioner that is a refrigeration apparatus according to an embodiment of the present invention. In FIG. 1, the air conditioner is an air conditioner that can perform a cooling operation or a heating operation, and includes an outdoor unit 20, an indoor unit 40, and a liquid refrigerant communication pipe for connecting the outdoor unit 20 and the indoor unit 40. 71 and a gas refrigerant communication pipe 72. Moreover, each apparatus of an air conditioning apparatus is controlled by the control part 80 (refer FIG. 6).

(1-2) Indoor Unit The indoor unit 40 includes an indoor heat exchanger 42 and an indoor fan 44. The indoor heat exchanger 42 is a cross-fin heat exchanger, and can evaporate or condense the refrigerant flowing inside by heat exchange with indoor air, thereby cooling or heating indoor air.

(1-2-1) Indoor Heat Exchanger The indoor heat exchanger 42 has a volume Vhi and includes heat transfer fins and heat transfer tubes. The heat transfer fin is a thin flat plate made of aluminum, and a plurality of through holes are formed in one heat transfer fin. The heat transfer tube is composed of a cylindrical straight tube inserted into the through hole of the heat transfer fin and a U-shaped tube that connects ends of adjacent straight tubes, and the total volume is the volume Vhi. The straight pipe is inserted into the through-hole of the heat transfer fin, and then is expanded by a pipe expander to be in close contact with the heat transfer fin.

(1-2-2) Indoor Fan The indoor fan 44 takes in indoor air by rotation and sends it to the indoor heat exchanger 42 to promote heat exchange between the indoor heat exchanger 42 and indoor air.

(1-3) Outdoor Unit In FIG. 1, the outdoor unit 20 mainly includes an accumulator 22, a compressor attached container 23, a compressor 24, a four-way switching valve 26, an outdoor heat exchanger 28, a large-diameter pipe 30, and an expansion. A valve 33, a liquid refrigerant side closing valve 37, and a gas refrigerant side closing valve 38 are provided, and these are connected by an outdoor unit refrigerant pipe 31. Furthermore, the outdoor unit 20 also has an outdoor fan 35.

(1-3-1) Compressor, Four-way Switching Valve, and Accumulator The compressor 24 sucks the gas refrigerant through the compressor accessory container 23 and compresses the gas refrigerant. An accumulator 22 is disposed in front of the compressor 24.

  The four-way switching valve 26 switches the direction of the refrigerant flow when switching between the cooling cycle and the heating cycle. During the cooling operation and the pump-down operation described later, the four-way switching valve 26 connects the refrigerant pipe on the discharge side of the compressor 24 and the gas side inlet / outlet of the outdoor heat exchanger 28 and is connected to the suction side of the compressor 24. The refrigerant pipe and the gas refrigerant side closing valve 38 are connected. That is, the cooling cycle state indicated by the solid line in the four-way switching valve 26 in FIG.

  Further, during the heating operation, the four-way switching valve 26 connects the refrigerant pipe on the discharge side of the compressor 24 and the gas refrigerant side closing valve 38, and also connects the refrigerant pipe on the suction side of the compressor 24 and the outdoor heat exchanger 28. Connect to the gas side doorway. That is, it is a heating cycle state indicated by a dotted line in the four-way selector valve 26 of FIG.

  The accumulator 22 is a container whose volume is the volume Va, and has a gas-liquid separation function for dividing the refrigerant into a gas phase and a liquid phase. The refrigerant flowing into the accumulator 22 is divided into a liquid phase and a gas phase, and the gas phase refrigerant gathered in the upper space flows out to the compressor 24.

(1-3-2) Outdoor heat exchanger The outdoor heat exchanger 28 is a stacked heat exchanger whose volume is a volume Vho, and condenses or evaporates the refrigerant flowing inside by heat exchange with outdoor air. be able to. The outdoor fan 35 is disposed so as to face the outdoor heat exchanger 28. When the outdoor fan 35 rotates, the outdoor air is taken in and blown to the outdoor heat exchanger 28, and heat between the outdoor heat exchanger 28 and the outdoor air is obtained. Promote exchange.

  FIG. 2 is an external perspective view of the outdoor heat exchanger 28. The outdoor heat exchanger 28 includes a flat multi-hole tube 53, insertion fins 54, and headers 51 and 52.

  The flat multi-hole tube 53 is formed of aluminum or an aluminum alloy, and has upper and lower flat portions serving as heat transfer surfaces and a plurality of internal flow paths 53a (see FIG. 3) through which a refrigerant flows. The flat multi-hole tubes 53 are arranged in a plurality of stages at intervals in a state where the plane portion is directed up and down.

  The insertion fins 54 are aluminum or aluminum alloy fins having the shape shown in FIG. 3 and are in contact with the flat multi-hole tube 53. The insertion fins 54 are formed with a plurality of notches 54 a extending horizontally so that the insertion fins 54 can be inserted into the multi-stage flat multi-hole pipes 53 arranged between the headers 51, 52. Has been. The shapes of the cutouts 54a of these insertion fins 54 substantially match the outer shape of the cross section of the flat multi-hole tube 53, as shown in FIG.

  The headers 51 and 52 are connected to both ends of flat multi-hole tubes 53 arranged in a plurality of stages in the vertical direction. The headers 51 and 52 have a function of supporting the flat multi-hole pipe 53, a function of guiding the refrigerant to the internal flow path 53a of the flat multi-hole pipe 53, and a function of collecting the refrigerant that has come out of the internal flow path 53a. doing. The header 51 is divided into four internal spaces by partition plates 51a, 51b, 51c. The header 52 is divided into five internal spaces by partition plates 52a, 52b, 52c, and 52d. In addition to the flat multi-hole pipe 53, the communication pipes 54 and 55 shown in FIGS. 4 and 5, the narrow pipes 57, 58 and 59 extending from the flow divider 29, and the outdoor unit refrigerant pipe in each internal space in the headers 51 and 52. 31 is connected.

  The volume Vho of the outdoor heat exchanger 28, which is the sum of the internal volume of the flat multi-hole tube 53 and the internal volumes of the headers 51 and 52, is smaller than the volume Vhi of the indoor heat exchanger 42. In other words, the volume Vhi of the indoor heat exchanger 42 is larger than the volume Vho of the outdoor heat exchanger 28.

  As shown in FIG. 5, the high-pressure gas refrigerant flowing from the compressor 24 in the cooling cycle operation flows into the upper space of the header 51 through the outdoor unit refrigerant pipe 31. This gas refrigerant flows through the flat multi-hole tube 53 to the upper three of the five internal spaces of the header 52, is folded back, and passes through the flat multi-hole tube 53 disposed on the lower side to form the header. It flows to the lower three of the four internal spaces of 51. The refrigerant liquefied when passing through the flat multi-hole pipe 53 is further collected from the three internal spaces below the header 51 through the thin pipes 57, 58 and 59 by the flow divider 29 and flows to the expansion valve 33. In the heating operation of the heating cycle, the flow direction of the refrigerant is reversed.

(1-3-3) Large-diameter pipe The large-diameter pipe 30 is a cylindrical pipe having a diameter larger than that of the outdoor unit refrigerant pipe 31, and is a pipe capable of storing surplus refrigerant. The volume of the large diameter tube 30 is a volume Vt.

The volume Vt, which is the volume of the large-diameter pipe 30, is relative to the volume Vhi of the indoor heat exchanger 42, the volume Vho of the outdoor heat exchanger 28, and the volume Va of the accumulator 22.
Formula: Volume Vt> Volume Vhi-Volume Vho-Volume Va
The diameter and length of the large diameter tube 30 are determined so as to satisfy the above. Here, the volume Vho of the outdoor heat exchanger 28 and the volume Va of the accumulator 22 are 1400 to 1600 cc, respectively, and the volume Vt of the large diameter tube 30 is about 300 cc.

  As shown in FIGS. 1 and 5, the large diameter pipe 30 is provided between the outdoor heat exchanger 28 and the liquid refrigerant side closing valve 37. Specifically, the large-diameter pipe 30 is disposed between the outdoor heat exchanger 28 and the expansion valve 33 in the outdoor unit 20. The large-diameter pipe 30 is arranged so as to extend long along the vertical direction, and has an upper end connected to the outdoor heat exchanger 28 and a lower end connected to the expansion valve 33. That is, the large-diameter pipe 30 is arranged so that the liquid refrigerant flows from the top to the bottom in the pump down operation described later. The large-diameter tube 30 is a simple cylindrical tube and does not have a gas-liquid separation function for separating the refrigerant into a gas phase and a liquid phase.

(1-3-4) Expansion Valve The expansion valve 33 is provided in the outdoor unit refrigerant pipe 31 between the large-diameter pipe 30 and the liquid refrigerant side shut-off valve 37 in order to adjust the refrigerant pressure and the refrigerant flow rate. It has a function of expanding the refrigerant in both operation and heating operation. The expansion valve 33 is an electric valve whose opening degree is adjusted according to a command from the control unit 80.

(1-3-5) Closing valve and refrigerant communication pipe The liquid refrigerant side closing valve 37 and the gas refrigerant side closing valve 38 are manual valves that are manually opened and closed, and are respectively a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe. 72. The liquid refrigerant communication pipe 71 connects the liquid side pipe of the indoor heat exchanger 42 of the indoor unit 40 and the liquid refrigerant side shut-off valve 37 of the outdoor unit 20. The gas refrigerant communication pipe 72 connects the gas side pipe of the indoor heat exchanger 42 of the indoor unit 40 and the gas refrigerant side closing valve 38 of the outdoor unit 20.

  The refrigerant communication pipes 71 and 72 allow the refrigerant to flow in the order of the compressor 24, the outdoor heat exchanger 28, the expansion valve 33, and the indoor heat exchanger 42 during the cooling cycle, and during the heating cycle, the compressor 24, the indoor The refrigerant flows in the order of the heat exchanger 42, the expansion valve 33, and the outdoor heat exchanger 28.

(1-4) Control Unit and Sensor The control unit 80 shown in FIG. 6 includes a microcomputer, a memory, and the like, and performs a pump-down operation for collecting refrigerant in the outdoor unit 20 in addition to a cooling operation and a heating operation. For this reason, the control unit 80 includes a cooling operation control unit 91, a heating operation control unit 92, a pump down operation control unit 93, and the like as functional units.

  Moreover, the air conditioning apparatus is provided with various sensors. Specifically, a discharge pressure sensor 81 for detecting the compressor discharge pressure in the refrigerant pipe on the discharge side of the compressor 24, a discharge temperature sensor 82 for detecting the compressor discharge temperature, and a compression in the refrigerant pipe on the suction side of the compressor 24 An intake temperature sensor 83 that detects the temperature of the refrigerant sucked into the machine 24, an outdoor heat exchanger temperature sensor 84 that detects the temperature of the refrigerant in the outdoor heat exchanger 28, and a room that detects the temperature of the refrigerant in the indoor heat exchanger 42. A heat exchanger temperature sensor 85 and the like are provided. The control unit 80 collects various data from these sensors 81 to 85 and uses it as information for controlling the operations of the outdoor fan 35, the expansion valve 33, the compressor 24, and the indoor fan 44 in each operation.

(2) Flow of refrigerant during heating operation In FIG. 1, during the heating operation, the four-way switching valve 26 is in a heating cycle state indicated by a dotted line. That is, the four-way switching valve 26 connects the refrigerant pipe on the discharge side of the compressor 24 and the gas refrigerant side shut-off valve 38, and the refrigerant pipe on the suction side of the compressor 24 and the refrigerant on the gas side of the outdoor heat exchanger 28. Connect the piping. Moreover, the opening degree of the expansion valve 33 is reduced. As a result, the outdoor heat exchanger 28 functions as a refrigerant evaporator, and the indoor heat exchanger 42 functions as a refrigerant condenser.

  In the refrigerant circuit in such a state, the low-pressure refrigerant is sucked into the compressor 24 and is discharged after being compressed to a high pressure. The high-pressure refrigerant discharged from the compressor 24 enters the indoor heat exchanger 42 through the four-way switching valve 26, the gas refrigerant side closing valve 38 and the gas refrigerant communication pipe 72. The high-pressure refrigerant that has entered the indoor heat exchanger 42 is condensed by exchanging heat with the indoor air. Thereby, indoor air is heated.

  Since the capacity Vhi of the indoor heat exchanger 42 is larger than the capacity Vho of the outdoor heat exchanger 28, most of the liquid refrigerant is accommodated in the condenser (indoor heat exchanger 42) during the heating operation. The high-pressure refrigerant condensed in the indoor heat exchanger 42 reaches the expansion valve 33 through the liquid refrigerant communication pipe 71 and the liquid refrigerant side closing valve 37.

  The refrigerant is decompressed to a low pressure by the expansion valve 33, and then enters the outdoor heat exchanger 28 through the large diameter pipe 30. The refrigerant passing through the outdoor heat exchanger 28 evaporates by exchanging heat with outdoor air supplied by the outdoor fan 35.

  The low-pressure refrigerant evaporated in the outdoor heat exchanger 28 is again sucked into the compressor 24 through the four-way switching valve 26.

(3) Flow of refrigerant during cooling operation and pump-down operation In FIG. 1, during the cooling operation and the pump-down operation, the four-way switching valve 26 is in a cooling cycle state indicated by a solid line. That is, the four-way switching valve 26 connects the discharge side of the compressor 24 and the refrigerant pipe on the gas side of the outdoor heat exchanger 28, and connects the refrigerant pipe on the suction side of the compressor 24 and the gas refrigerant side closing valve 38. Connecting. Moreover, the opening degree of the expansion valve 33 is reduced. As a result, the outdoor heat exchanger 28 functions as a refrigerant condenser, and the indoor heat exchanger 42 functions as a refrigerant evaporator.

  In the refrigerant circuit in such a state, the low-pressure refrigerant is sucked into the compressor 24 and is discharged after being compressed to a high pressure. The high-pressure refrigerant discharged from the compressor 24 is sent to the outdoor heat exchanger 28 through the four-way switching valve 26.

  The high-pressure refrigerant sent to the outdoor heat exchanger 28 is condensed by exchanging heat with outdoor air. The high-pressure refrigerant condensed in the outdoor heat exchanger 28 is sent to the expansion valve 33 through the large diameter pipe 30. In addition, since the capacity | capacitance Vho of the outdoor heat exchanger 28 is smaller than the capacity | capacitance Vhi of the indoor heat exchanger 42, a condenser (outdoor heat exchanger 28) accommodates all the liquid refrigerants at the time of cooling operation and pump down operation. I can't. Therefore, during the pump-down operation, liquid refrigerant that cannot be accommodated in the outdoor heat exchanger 28 accumulates in the large-diameter pipe 30, and the large-diameter pipe 30 is filled with liquid refrigerant (see FIG. 5).

  The liquid refrigerant that has exited the large-diameter pipe 30 is sent to the expansion valve 33 and depressurized to a low pressure. The low-pressure refrigerant decompressed by the expansion valve 33 enters the indoor heat exchanger 42 through the liquid refrigerant side closing valve 37 and the liquid refrigerant communication pipe 71.

  The low-pressure refrigerant that has entered the indoor heat exchanger 42 exchanges heat with room air and evaporates there. Thereby, indoor air is cooled. The low-pressure refrigerant evaporated in the indoor heat exchanger 42 is again sucked into the compressor 24 through the gas refrigerant communication pipe 72, the gas refrigerant side closing valve 38, and the four-way switching valve 26.

(4) Pump-down operation As described above, the pump-down operation is an operation performed with the four-way switching valve 26 in a cooling cycle state indicated by a solid line, as in the cooling operation. The control unit 80 performs the pump-down operation of containing the refrigerant in the indoor unit 40 and the refrigerant communication pipes 71 and 72 in the outdoor unit 20 in four steps shown in FIGS. 7 and 8.

  In the pump-down operation, first, an activation step is started (step S1 in FIG. 8). In the starting step, the motor of the compressor 24 is rotated at 60 rps (60 revolutions per second), and the opening degree of the expansion valve 33 is set to 300 pls (pulses given to the motor for adjusting the opening degree of the expansion valve 33). The outdoor fan 35 and the indoor fan 44 are rotated at a predetermined rotational speed. Note that, as in normal operation, the liquid refrigerant side closing valve 37 and the gas refrigerant side closing valve 38 at this time are open.

  When 120 seconds elapse from the start of the starting step, the process proceeds to step S2, and the first liquid reservoir step is started. In the first liquid reservoir step, the motor of the compressor 24 is rotated at 30 rps, which is lower than the rotational speed of the compressor 24 at the start-up step. The opening degree of the expansion valve 33 is set so as to be larger than that in the starting step (here, 500 pls). The outdoor fan 35 continues to rotate at a predetermined rotational speed, but the indoor fan 44 is stopped. Since the indoor fan 44 is stopped, in the first liquid reservoir step, the wet gas refrigerant that has not been evaporated in the indoor unit 40 flows to the outdoor unit 20 and is separated into gas and liquid by the accumulator 22. Of the refrigerant gas-liquid separated by the accumulator 22, the gas refrigerant flows to the compressor 24, and the liquid refrigerant accumulates inside the accumulator 22.

  When 300 seconds elapse from the start of the first liquid reservoir step, the process proceeds to step S3, and the pressure reduction step is started. In the pressure reduction step, the rotational speed of the motor of the compressor 24 is not changed, the outdoor fan 35 continues to rotate at a predetermined rotational speed, and the indoor fan 44 continues to stop. In the pressure drop step, the opening degree of the expansion valve 33 is set to 200 pls during the first 60 seconds and to 100 pls during the second 60 seconds. In this way, the internal pressure of the accumulator 22 is lowered stepwise by gradually reducing the opening degree of the expansion valve 33 (approaching the fully closed state) in the pressure reduction step. Thereby, it is suppressed that the liquid refrigerant collected inside the accumulator 22 foams under reduced pressure.

  When the 120 second pressure reduction step is completed, the process proceeds to step S4, and the second liquid reservoir step is started. The control unit 80 changes only the opening degree of the expansion valve 33 without changing the states of the compressor 24, the outdoor fan 35, and the indoor fan 44. Specifically, the opening degree of the expansion valve 33 is set to 0 pls, and the expansion valve 33 is fully closed. Then, after the start of the second liquid reservoir step, the control unit 80 notifies the operator that the liquid refrigerant side closing valve 37 is closed. Here, an LED (not shown) that can be confirmed by the operator is turned on to prompt the operator to close the liquid refrigerant side closing valve 37 (step S5). As a result, the second liquid reservoir step is started in a state where the operator closes the liquid refrigerant side closing valve 37 and closes the liquid refrigerant side closing valve 37. Here, since the expansion valve 33 and the liquid refrigerant side closing valve 37 are closed, the refrigerant sent from the compressor 24 to the outdoor heat exchanger 28 is condensed and liquefied in the outdoor heat exchanger 28. Then, it accumulates in the large diameter tube 30 and the outdoor heat exchanger 28. FIG. 5 shows a state when the liquid refrigerant is accumulated in the large-diameter pipe 30 and the outdoor heat exchanger 28.

  In step S6, it is determined whether or not an end condition for the second liquid reservoir step is satisfied. Here, a condition that the process is terminated when the refrigerant temperature on the discharge side of the compressor 24 exceeds a predetermined temperature is adopted as the termination condition. As the end condition, it may be adopted that a predetermined time has elapsed from the start of the second liquid reservoir step, or that the refrigerant temperature on the suction side of the compressor 24 has become a predetermined temperature or less.

(5) Features of the air conditioner (5-1)
In this air conditioner, the volume Vhi of the indoor heat exchanger is larger than the volume Vho of the outdoor heat exchanger, but the outdoor unit 20 includes a large-diameter pipe 30 that is not found in a conventional apparatus. The volume Vt of the large-diameter pipe 30 is made larger than the volume Vhi of the indoor heat exchanger 42 minus the volume Vho of the outdoor heat exchanger 28 and the volume Va of the accumulator 22. In particular,
Formula: Volume Vt> Volume Vhi-Volume Vho-Volume Va
The diameter and length of the large-diameter tube 30 are determined so as to satisfy the above.

  Thereby, a refrigerant | coolant can be suitably collected by the outdoor unit 20 by a pump down driving | operation.

(5-2)
In this air conditioner, the accumulator 22 provided in the conventional apparatus has the same gas-liquid separation function as the conventional one, but the large-diameter pipe 30 does not have the gas-liquid separation function. The large-diameter pipe 30 is a simple cylindrical pipe, and can be manufactured and assembled at low cost, so that the cost increase of the air conditioner can be reduced.

  The large-diameter pipe 30 is disposed so as to extend long in the vertical direction, and the upper end is connected to the outdoor heat exchanger 28 and the lower end is connected to the expansion valve 33. Thereby, in the pump-down operation, the liquid refrigerant flows from the top to the bottom of the large-diameter pipe 30, and the liquid refrigerant is easily collected in the internal space of the large-diameter pipe 30.

(5-3)
In this air conditioner, the large-diameter pipe 30 is disposed between the outdoor heat exchanger 28 and the expansion valve 33, and the expansion valve 33 is fully closed at the start of the second liquid reservoir step of the pump-down operation. Yes. For this reason, liquid refrigerant accumulates in the large diameter pipe 30 and the outdoor heat exchanger 28 before the operator closes the liquid refrigerant side closing valve 37 during the second liquid reservoir step. Thereby, the time of pump down operation is shortened.

(5-4)
When collecting refrigerant by the pump-down operation in the outdoor unit, in the case of a conventional apparatus, the refrigerant is sent from the compressor to the outdoor heat exchanger with the liquid refrigerant side shut-off valve closed. However, the refrigerant hardly accumulates in the accumulator provided in the suction side piping of the compressor.

  In this air conditioner, the first liquid storage step for storing the refrigerant in the accumulator 22 is performed prior to the second liquid storage step that is performed with the liquid refrigerant side closing valve 37 closed. As described above, in the pump down operation, the liquid refrigerant side closing valve 37 is opened to draw the wet gas refrigerant from the indoor heat exchanger 42, and the liquid refrigerant side closing valve 37 is closed to the outdoor heat exchanger 28. Since the refrigerant is stored in each part of the outdoor unit 20 in the order of the second liquid storage step for sending the refrigerant and the refrigerant, the situation in which the refrigerant cannot be stored in the outdoor unit 20 can be avoided.

(5-5)
In this air conditioner, the control unit 80 executes the pressure reduction step after the first liquid reservoir step and before the second liquid reservoir step in the pump down operation. In the pressure lowering step, the refrigerant pressure inside the accumulator 22 decreases stepwise by changing the opening of the expansion valve 33.

  If the first liquid storage step suddenly shifts to the second liquid storage step in which the liquid refrigerant side closing valve 37 is closed, the liquid refrigerant stored in the accumulator 22 may be decompressed and foamed.

  However, here, since the pressure drop step is provided between the first liquid reservoir step and the second liquid reservoir step, the liquid refrigerant in the accumulator 22 accumulated in the first liquid reservoir step is foamed and is accumulated in the accumulator 22. The amount of refrigerant is almost never reduced.

(5-6)
In this air conditioner, when the control unit 80 starts the second liquid reservoir step, the opening degree of the expansion valve 33 is set to the lower limit value, and the expansion valve 33 is fully closed. Furthermore, the control unit 80 prompts the operator to close the liquid refrigerant side closing valve 37 so that the liquid refrigerant side closing valve 37 is closed after the opening degree of the expansion valve 33 reaches the lower limit value. Information is being given.

  Thus, in the second liquid reservoir step, the refrigerant sent from the compressor 24 to the outdoor heat exchanger 28 flows toward the indoor unit 40 even before the liquid refrigerant side closing valve 37 is closed. There is no. Further, the notification timing for prompting the closing operation of the liquid refrigerant side closing valve 37 is set to a timing at which the manual closing operation of the liquid refrigerant side closing valve 37 is performed after the expansion valve 33 is fully closed. Yes. For this reason, the situation that the liquid refrigerant side closing valve 37 is manually closed before the expansion valve 33 is fully closed is avoided, and the reduced pressure foaming suppression function of the pressure lowering step works appropriately.

(5-7)
In this air conditioner, a pressure reduction step is provided in order to suppress decompression foaming in the accumulator 22, but if the pressure reduction step takes too much time, the total time required for the pump-down operation becomes long. Therefore, the control unit 80 of the air conditioner ends the pressure reduction step after a predetermined time (120 seconds) has elapsed. Thereby, the situation where the time of a pressure fall step becomes long can be avoided.

(5-8)
In the first liquid reservoir step, the wet gas refrigerant is drawn from the indoor heat exchanger 42 with the liquid refrigerant side closing valve 37 and the expansion valve 33 opened, and the accumulator 22 stores the refrigerant. If the state of pulling the gas refrigerant is continued for a long time, the liquid refrigerant that cannot be stored in the accumulator 22 may flow to the compressor 24.

  Therefore, in this air conditioner, the control unit 80 ends the first liquid reservoir step after a predetermined time (300 seconds) has elapsed. The time of 300 seconds is a time in which the time for which the refrigerant is accumulated in the accumulator 22 is examined in advance by a test and is incorporated in the control unit 80. Thereby, the malfunction that a liquid refrigerant flows from the accumulator 22 to the compressor 24 and the compressor 24 is damaged in the pump down operation can be avoided.

  In addition, although it is the predetermined time which complete | finishes a 1st liquid reservoir step, suitable time changes with the structure of an air conditioning apparatus.

(5-9)
The controller 80 of the air conditioner performs the number of rotations of the compressor 24 in the first liquid reservoir step before performing the first liquid reservoir step different from the normal operation of drawing the wet gas refrigerant from the indoor heat exchanger 42 (see FIG. The starting step for operating the compressor 24 at a rotational speed (60 rps) higher than 30 rps) is executed. Since the start-up step close to the normal operation is performed at the beginning of the pump-down operation, the behavior of the refrigerant in the first liquid reservoir step is stabilized, and is less influenced by the air conditioner and the state of the refrigerant before the pump-down operation. The steps after the first liquid reservoir step are executed satisfactorily.

(6) Modification (6-1)
In the above embodiment, the pressure reduction step is terminated after a predetermined time (120 seconds) has elapsed. However, in order to reduce the time required for the pressure reduction step, the following may be performed.

  In this modification, a suction pressure sensor is newly provided in the refrigerant pipe on the suction side of the compressor 24, and based on the output value of the suction pressure sensor, the opening degree of the expansion valve 33 is changed in the pressure reduction step and the pressure reduction step. Determine the end of. In this case, the opening degree of the expansion valve 33 is reduced stepwise so that the liquid refrigerant in the accumulator 22 does not foam under reduced pressure based on the output value of the suction pressure sensor that indicates the internal pressure of the accumulator 22. When the value of the suction pressure sensor becomes so small that the expansion valve 33 is not fully foamed even when the opening degree of the expansion valve 33 is fully closed, the pressure reduction step is terminated and the process proceeds to the second liquid reservoir step. Thereby, although it is necessary to newly provide a suction pressure sensor, the time required for the pressure drop step can be shortened.

(6-2)
In the above-described embodiment, the notification that prompts the operator to close the liquid refrigerant side shut-off valve 37 after starting the second liquid reservoir step is performed by turning on an LED (not shown). Alternatively, if there is another notification means, it may be performed using it.

(6-3)
In the above embodiment, a laminated heat exchanger having the flat multi-hole tube 53, the insertion fins 54, and the headers 51 and 52 is adopted as the outdoor heat exchanger 28. However, the laminated heat having another structure is used. An exchanger can also be employed.

  For example, the heat exchanger 128 having the flat multi-hole tube 153, the corrugated fin 154, and the headers 151 and 152 shown in FIG. The corrugated fins 154 are aluminum or aluminum alloy fins bent into a corrugated shape. The corrugated fins 154 are disposed in the ventilation space sandwiched between the flat multi-hole pipes 153 that are vertically adjacent to each other, and the valley portions and the mountain portions are in contact with the flat portions of the flat multi-hole pipes 153.

20 Outdoor unit (heat source side unit)
22 Accumulator (refrigerant container)
24 Compressor 28, 128 Outdoor heat exchanger (heat source side heat exchanger)
30 Large diameter pipe 31 Refrigerant pipe 33 Expansion valve 37 Liquid refrigerant side closing valve 38 Gas refrigerant side closing valve 40 Indoor unit (use side unit)
42 Indoor heat exchanger (use side heat exchanger)
53,154 Flat multi-hole tube (flat tube)
54,154 fins (heat transfer fins)
71 Liquid refrigerant communication pipe 72 Gas refrigerant communication pipe 80 Control section

JP-A-6-143991

Claims (7)

Liquid refrigerant side closing valve (37), gas refrigerant side closing valve (38), compressor (24), heat source side heat exchanger (28, 128), and heat source side for blowing air to the heat source side heat exchanger A heat source side unit (20) having a fan (35), an expansion valve (33), and an accumulator (22) provided in a suction side pipe of the compressor;
One end is connected to the liquid refrigerant side closing valve (37) via a liquid refrigerant communication pipe (71) and the other end is connected to the gas refrigerant side closing valve (38) via a gas refrigerant communication pipe (72). A use side unit (40) having a side heat exchanger (42) and a use side fan (44) for blowing air to the use side heat exchanger ;
A control unit (80) for performing a pump-down operation for collecting the refrigerant in the heat source side unit (20);
With
The control unit (80)
In the pump-down operation, in order, the start step, the first liquid reservoir step, the second liquid reservoir step,
In the first liquid reservoir step after the start-up step, the use-side fan that has been operated at the rotation speed lower than the rotation speed of the compressor in the start-up step and has been turned in the start-up step (44) is stopped, and the liquid refrigerant side closing valve (37) is opened, and the wet gas refrigerant is drawn from the use side heat exchanger (42) via the gas refrigerant communication pipe (72). Let the accumulator (22) store the refrigerant ,
In the second liquid reservoir step after the first liquid reservoir step, the compressor (24) to the heat source side heat exchanger (28, 128) with the liquid refrigerant side shut-off valve (37) closed. The refrigerant is sent to the heat source side heat exchanger (28, 128) to accumulate the refrigerant,
Refrigeration equipment. The expansion valve (33) is an electric valve arranged between the heat source side heat exchanger (28, 128) and the liquid refrigerant side closing valve (37),
In the pump-down operation, the controller (80) changes the opening of the expansion valve (33) stepwise after the first liquid reservoir step and before executing the second liquid reservoir step. Performing a pressure reduction step for reducing the refrigerant pressure in the accumulator (22).
The refrigeration apparatus according to claim 1. The liquid refrigerant side closing valve (37) is a manual valve,
The controller (80) sets the opening degree of the expansion valve (33) to a lower limit value when the second liquid reservoir step is started or immediately before the start, and sets the opening degree of the expansion valve (33) to a lower limit value. A notification for urging the operator to close the liquid refrigerant side closing valve (37) is performed so that the closing operation is performed.
The refrigeration apparatus according to claim 2. The controller is
Ending the pressure drop step after a predetermined time,
Or
Based on an output value of a pressure sensor provided in a suction side pipe of the compressor, a change in the opening of the expansion valve in the pressure reduction step and an end of the pressure reduction step are determined.
The refrigeration apparatus according to claim 2 or 3. The controller (80) ends the first liquid reservoir step after a predetermined time has elapsed.
The refrigeration apparatus according to any one of claims 1 to 4. The control unit (80) further increases the opening of the expansion valve in the first liquid reservoir step than in the startup step.
The refrigeration apparatus according to any one of claims 1 to 5. The volume of the heat source side heat exchanger (28, 128) is a volume Vho,
The volume of the use side heat exchanger (42) is a volume Vhi, which is larger than the volume Vho.
The refrigeration apparatus according to any one of claims 1 to 6.

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